Tetra-O-alkylated hydrophobic 2-phenylthiohydroquinone dimers were prepared by the Fe(III)-mediated oxidative dimerization. The prepared dimers were soluble in hexane and served as fluorescent dyes in the hydrophobic solvent. Their physical properties were also examined.

Sorbitol was effectively converted to isosorbide by treatment with [TMPA][NTf₂] in the presence of catalytic amounts of TsOH under microwave heating at 180 °C. The reaction completed within 10 min and isosorbide was isolated to about 60 %. Ionic liquids were readily recovered by an extraction treatment and reused several times.

An efficient transformation of polyamides to ω-hydroxy alkanoic acids was achieved. Treatment of nylon-12 with supercritical MeOH in the presence of glycolic acid gave methyl ω-hydroxydodecanoate in 85 % yield and the alcohol/alkene selectivity in the product was enhanced to up to 9.5:1. The use of ¹⁸O-enriched acetic acid for the reaction successfully introduced an ¹⁸O atom at the alcoholic OH group in the product. This strategy may provide a new and economical solution for the chemical recycling of waste plastics.

The Heck–Matsuda reaction for allylic nitro compounds effectively afforded cinnamyl nitro compounds in good yields. Aryldiazonium salts that have an electron-donating substituent underwent a smooth reaction in the presence of Pd₂dba₃. A palladium complex that coordinated with an electron-rich ligand was necessary for the reaction to progress with electron-deficient aryldiazonium salts. An optically active allylic nitro compound underwent reaction without the loss of optical purity at the stereogenic center. A short synthesis of an optically active FTY720 derivative was achieved by this method.

Waste fiber-reinforced plastics (FRP) and unsaturated polyesters were readily depolymerized by subjecting them to a treatment with ionic liquids under heating conditions. The use of microwaves for heating effectively progressed depolymerization, whereas the conventional heating method was ineffective for this purpose. We isolated the monomeric material, phthalic anhydride, by direct distillation from the reaction pot under reduced pressure with yields of more than 90 %. We recovered the glass fibers in a pure form and achieved the effective removal of polystyrene, the linker unit of FRP. Ionic liquids were useful for several iterations of the reaction, and purification of the used ionic liquids was also possible. Thus, we developed a new use of ionic liquids for chemical recycling of waste plastics.

Treatment of a polyamide such as Nylon-6 in ionic liquids at 300°C resulted in the effective depolymerization to monomeric amides, which were readily isolated through direct distillation from the reaction pot. The ionic liquids were recycled and they still worked as good reaction media after being used five times. The present method provides a new usage of ionic liquids that will serve as a key material for realizing zero-emission chemical recycling process of plastics. Copyright © 2008 John Wiley & Sons, Ltd.

Waste fiber-reinforced plastics (FRPs), which are formidable composite plastics for chemical treatment, can be efficiently depolymerized by treatment with supercritical methanol in the presence of catalytic amounts of 4-(dimethylamino)pyridine (DMAP), which is a well-known catalyst for the formation of esters and amides. This novel depolymerization reaction also provides ready separation of the depolymerized products into three components: methanol-soluble oil, CHCl₃-soluble solid, and an inorganic residue. Thus, almost complete decomposition of FRP as well as useful separation of the decomposed products was achieved with the present method, and the latter were ready for chemical recycling. Investigation of the reaction profile revealed that the reaction rate increased as the amount of DMAP increased. Unfortunately, DMAP employed in the reaction could not be recovered because of its decomposition catalyzed by dimethyl phthalate, a depolymerized product from waste FRP, under the reaction conditions employed.